Can mold grow on food packed in oil?

December 14, 2008 4:35 PM

Can mold grow on food packed in oil?

There's some "Can I eat this?" context here, but I've fairly well decided at this point not to eat the food in question (some roasted bell peppers that I attempted to preserve 6 weeks ago in a refrigerated jar of canola oil), since having read elsewhere that oil-packing will not prevent the growth of botulism unless the packed food is properly dried and/or acidulated.

But can the white spots which recently appeared on those peppers really be mold? If so, then one of two principles I had thought to be true must be upset: that mold requires oxygen to grow, and that submerging food in oil creates a seal which is impermeable to oxygen. On the other hand, if these spots aren't mold, what else might they be? (Sorry, I would provide a photo if I had a working digital camera...)

Finally, the next time a peck of peppers tumbles my way, what might I do differently to preserve them safely? Is there any way to do it that isn't tantamount to pickling them (and thus changing their flavor significantly)?

posted by aws17576 to food & drink (10 comments total)

Mold can grow at very low levels of oxygen, however the white spots on your peppers are probably colonies of anaerobic bacteria. Botulism is caused by a type of bacteria, not mold.

Don't eat them.
posted by 517 at 4:47 PM on December 14, 2008

They probably are mold. I eat a lot of oil-preserved pickles and they invariably develop mold sooner or later. The oil does help to retard its growth, but there's still a non-zero chance.
posted by peacheater at 4:47 PM on December 14, 2008

I got mold in a jar of oil-packed sun-dried tomatoes. I scooped out the top layer and used the lower ones with no noticable ill effects. That said, I'm probably never buying the Costco jar of sun-dried tomatoes again unless I am planning some kind of festival.
posted by mzurer at 4:52 PM on December 14, 2008

They may be mold; they may not be mold.

One thing that can happen with certain types of oil is that it can congeal in a refrigerator that is close to freezing. I've seen this happen often with my Newman's Own balsamic vinaigrette. So, try scraping some of the white off with a spoon, and give it ten minutes or so to come up to room temperature.

Pictures: 1, 2
posted by Maxwell_Smart at 4:54 PM on December 14, 2008

if a tiny bit peeks out of the oil it can/will get moldy. this happened to my lemons, which i had intended to be preserved in olive oil, but left some peeking out.
posted by luriete at 5:04 PM on December 14, 2008

You can freeze peppers. It changes texture but the flavor is still there. I do that when bell peppers are at there cheapest at the farmer's market.
posted by SuzySmith at 6:06 PM on December 14, 2008

I've seen furry stuff grow on top of the oil before (not my fridge, but that's another story,) I assume it was a mold, but it may have been some other type of nasty stuff. Either way, I didn't eat it then, and I wouldn't eat it in the future.
posted by paisley henosis at 6:29 PM on December 14, 2008

I read somewhere that things can mold in oil if there are tiny pockets of air left sealed within veggies. It becomes a tiny anaerobic environment that can breed all yuck stuff. Not really an answer, but my two cents.
posted by Bearded Dave at 8:48 AM on December 15, 2008

Many types of bacteria are quiet happy to grow without oxygen - in fact the bacteria that makes botulism toxin won't grow if there is oxygen. Bacteria aren't technically mold, but from a food safety perspective they're just as bad or worse - and bacteria love to form little white colonies/spots. Extreme heat (look up resources on canning) will kill most bacteria and molds, so your food will be safe as long as it hasn't been open.
posted by fermezporte at 4:16 PM on December 15, 2008

Finally, the next time a peck of peppers tumbles my way, what might I do differently to preserve them safely? Is there any way to do it that isn't tantamount to pickling them (and thus changing their flavor significantly)?

I'd advise sautéing and freezing the peppers. Clean and cut then sauté at medium high temp in oil to sweat out the water, then bag them up into measured portions and freeze. I've done this with peppers, mushrooms, onions, shallots, leeks, garlic, and assorted aromatic herbs with good results. Stored this way, your flavorful foods can't be the star performer of the dish, but still good enough to add body to pastas, stir frys, soups, stews, and sauces.

If you just want the flavor, roast your peppers then completely desiccate them, either by oven, dehydrator, or chemical desiccant, then mill into a powder to use as seasoning in your recipes. I work with a chef who uses roasted, dried, and powdered red peppers for their color and flavor to good results. This preparation can lead to interesting rubs or spice mixes.
posted by peeedro at 1:18 AM on December 19, 2008